1. Field of the Invention
An embodiment of this invention generally relates to a composite structure in which a structure containing a polycrystal comprising a brittle material is formed on a surface of a base material and a production method thereof.
2. Description of the Related Art
A method called aerosol deposition is disclosed in Patent Reference 1 as a method for forming a structure of a brittle material on a surface of a base material without any heating process and has widely been accepted.
The aerosol deposition method is characterized by injecting from a nozzle to a base material an aerosol obtained by dispersing fine particles of a brittle material or the like into a gas; bonding the brittle material fine particles by causing the fine particles to collide with the base material made from a metal, glass, ceramics, or a plastic to have the brittle material fine particles deformed or crushed by impact of the collision; and directly forming a structure formed of formation materials of the fine particles on the base material. The aerosol deposition method is capable of forming a structure particularly at an ordinary temperature that does not require any heating means as well as of obtaining a structure having mechanical strength similar to that of a sintered body.
Also, Patent Reference 2 discloses collision of superfine particles that are injected as being accelerated by electrostatic field or gas feeding with superfine particles on a substrate.
Non-patent Reference 1 discloses that surface roughness of a substrate influences on film formation. Specifically, it has been reported that: it is impossible to form a film when average surface roughness (Ra) of a ceramic base material is 56 nm; it is possible to form a film when the average surface roughness (Ra) is 142 nm; and, when the average surface roughness is 376 nm, film peeling occurs when a film thickness is 10 μm or more though it is possible to form a film.    [Patent Reference 1] WO01/027348    [Patent Reference 2] JP-A-2001-3180    [Non-patent Reference 1] Accomplishment Report on Commissioned Business of Independent Administrative Agency, New Energy and Industrial Technology Development Organization; Title: Accomplishment Report of 2001 to 2003, <Lead Phase> Research and Development of Fundamental Technologies for Effective Energy Use, Research and Development on Energy Rationalization Technology of Ceramic Engineering Process Utilizing Impact Bonding Effect